SwiftUI: Update Tab Bar Badge when Core Data item is added-CodePudding

This Problem drives me nuts: I have a small SwiftUi iOS App which works with Core data. All works fine, I can add edit etc. But the app is tab bar based ad I want one tabs badge updated when a record is added to core data.

So I thought I listen to the viewontext.hasChanged bool:

struct MainView: View {
   @Environment(\.managedObjectContext) private var viewContext
   @State var nrOfItems = 0
   let persistanceController : PersistenceController

   var body: some View {
      TabView{
         ItemListView(persistance: PersistenceController.shared)
            .tabItem{
               Label("Lebensmittel",systemImage: "cart")
            }
            .badge(nrOfItems)
      }
      .onChange(of: viewContext.hasChanges, perform: {newValue in
         nrOfItems = persistanceController.getRecordsCount()
      })
   }
}

But the code in onChange is never called ... and I can't find anything about it neither here nor somewhere else. Anyone any hints?

Thanks, Andreas

CodePudding user response：

The hasChanges is not published property, so it does not trigger onChange, try instead to use notification directly, like


.onReceive(NotificationCenter.default.publisher(for: NSManagedObjectContext.didChangeObjectsNotification, 
                                             object: viewContext)) { _ in
  nrOfItems = persistanceController.getRecordsCount()

}